Method for manufacturing hollow plastic articles



Oct. 22, 1968 'c. v. FOGELBERG ET AL 3,407,250

METHOD FOR MANUFACTURING HOLLOW PLASTIC ARTICLES Original Filed March25, 1963 7 Sheets-Sheet 1 FIGURE I.

INVENTORS CLEMENT V. FOGELBERG WILLIAM D. HOU H Oct. 22, 1968 c. v.FOGELBERG ET AL 3,407,250

METHOD FOR MANUFACTURING HOLLOW PLASTIC ARTICLES Original Filed March25, 1963 '7 Sheets-Sheet 2 INVENTORS CLEMENT V. FOGELBERG WiLLIAM D.HOUGH BY WWW ATTORNEYS Oct. 22, 1968 c. v. FOGELBERG ET AL 3,407,250

METHOD FOR MANUFACTURING HOLLOW PLASTIC ARTICLES Original Filed March25, 1963 7 Sheets-Sheet 5 INVENTORS CLEMENT V- FOGELBERG WILLIAM D. HOUH BY 2% r ATTORNEYS Oct. 22, 1968 c. v. FOGE'LBERG ET AL 3,407,250

METHOD FOR MANUFACTURING HOLLOW PLASTIC ARTICLES Original Filed March25, 1965 7 Sheets-Sheet 4 I Q r j FIG. 8

INVENTORS CLEMENT V. FOGELBERG ATTOR N EYS Oct. 22, 1968 c. v, FOGELBERGET AL 3,407,250

METHOD FOR MANUFACTURING HOLLOW PLASTIC ARTICLES Original Filed March25, 1963 '7 Sheets-Sheet .5

FIG. 9

INVENTORS CLEMENT v. FOGELBERG WILLIAM D GH HQU BY w (52M ATTORNEYS Oct.22, 1968 c. v. FOGELBERG ET L 3,407,250

METHOD FOR MANUFACTURING HOLLOW PLASTIC ARTICLES Original Filed March25, 1963 7 Sheets-Sheet 6 06 FIG. [2 99 INVENTORS CLEMENT V. FOGELBERGWILLIAM D HOU H ATTORNEYS METHOD FOR MANUFACTURING HOLLOW PLASTICARTICLES Original Filed March 25, 1963 '7 Sheets-Sheet 7 FIGURE 3]INVENTORS CLEMENT V FOGELBERG WILLIAM D. HOUGH BY ""J ATTOI RNEYS UnitedStates Patent 3,407,250 METHOD FOR MANUFACTURING HOLLOW PLASTIC ARTICLESClement V. Fogelberg, Boulder, and William D. Hough,

Denver, Colo., assignors to Ball Brothers Company Incorporated, Muncie,Ind., a corporation of Indiana Original application Mar. 25, 1963, Ser.No. 268,515, now Patent No. 3,257,687, dated June 28, 1966. Divided andthis application Feb. 1, 1966, Ser. No. 541,043

3 Claims. (Cl. 264-99) This application is a divisional application ofClement V. Fogelberg et al. application Ser. No. 268,515, filed Mar. 25,1963 now Patent No. 3,257,687.

This invention relates to a new and improved method and apparatus formolding plastic articles and particularly to a novel method andapparatus for molding hollow plastic articles such as containers orbottles by the blow molding principle.

The growth of the plastic article industry in recent years has made itnecessary for manufacturers not only to produce articles at highproduction rates, but also to produce a great variety of articles whichmay vary widely in size, shape, or weight. Although the extrusion ratesof commercial extrusion machines may be varied within wide limits, andthe nozzles of the machines may be altered to produce parisons or tubesof widely varying diameters and peripheral shapes, such flexibility hasnot been attainable with previous molding equipment. As a result, it wasimpossible heretofore to produce both large articles and small articlescontinuously on the same machine and still retain a high rate ofproduction.

It is well known that a small article normally requires a parison ofless material than does a large article and that it takes aproportionately longer time to extrude a large article than it does asmaller article with less material. However, the duration of the moldingcycle for the large article is usually not proportionately longer thanthe molding cycle for the smaller article but rather is of relativelyshorter duration. Therefore, manufacturers were faced with the problemof designing molding apparatus capable of utilizing many mold stationswith one extruder, which apparatus also permits adjustment of themolding capacity of the stations to efliciently utilize the lowerextrusion or parison-producing rate of a particular extrusion machinewhen large articles are being produced.

In view of the shortcomings and difficulties encountered with previousmolding methods and apparatus, it was totally unexpected and surprisingto discover a new and improved method and apparatus for molding hollowplastic articles which not only overcome the above problems but alsoeffectively utilize the most rapid extrusion rates practicable. Anadditional advantage of the invention is the great flexibility ofoperation which permits the production of articles varying widely insize, shape and weight. Moreover, the new and improved method andapparatus of the invention permit the transfer of a length of extrudedtubing, hereinafter referred to as a parison, from an extrusion nozzleto a mold station so as to minimize sagging or stretching of the parisondue to its suspension in a normally hot and formable condition. Afurther advantage of the apparatus of the invention is that the parisoncan be accurately positioned within a blow mold prior to the closingthereof. Also, thepresent invention provides a simple and convenientmeans for removing molded articles from a mold station.

Other advantages and features of the invention will be apparent from thefollowing description and drawings, in which:

FIGURE 1 is a side view of a mold station of the present invention;

3,407,250 Patented Oct. 22, 1968 FIGURE 2 is a front view of a moldstation;

FIGURE 3 is a plan view of a mold station;

FIGURES 4, 5, and 6 are enlarged plan views of a parison orienterportion of a mold station;

FIGURE 7 is a sectional view taken along line 77 of FIGURE 8;

FIGURE 8 is a side view of a portion of the transfer assembly;

FIGURE 9 is a perspective view of a portion of a mold station;

FIGURE 10 is a plan view of a parison positioner por-' tion of a moldstation and its relationship to the mold;

FIGURES 11 and 12 are side views of a parison positioner showing itsextreme positions during operation; and

FIGURE 13 is a side view of a blow stick assembly of a mold station.

As shown in the drawings, the frame 10 has wheels 13 secured to thelower portion thereof, which wheels are in contact with rails 14radially carried by members 17 and 18. Each mold station may be firmlyfixed upon the rails 14 by engagement of a rod 15 carried by the moldstation, which rod passes through an appropriate opening in one of therails 14.

A vertical support 11 projects upwardly from the mold station and hassecured thereto a horizontal member 12 which serves as a support for atransfer mechanism to be described. Member 12 has pivot points 22 and 23to which are attached a pair of movable parallel arms 20 and 21. Thesearms are pivotably joined at their opposite ends by a member 24 whichholds arms 20 and 21 parallel throughout their arcuate movement so thatmember 24 is always horizontally disposed and parallel to the uppermember 12. Thus, the combination of members 12 and 24 and arms 20 and 21form a mechanical pantograph device. An air cylinder 27 is attached tosupport 11 and arm 20 and on directed impulse moves the pantographassembly through the arc path. 7

A jaw structure comprising a pair of hinged jaws 30 and 31 is pivotablyattached to the member 24 and moves with it through a are path in ahorizontal attitude. The movement of the jaws is in a short are pathabout a vertical axis.

As shown in FIGURES 7 and 8, a pair of vertical supports 33 and 34having extensions 35 and 36 thereon are securely fastened to each of thehinged jaws 30 and 31. Each support is pivotably attached to member 24by pins 37 and 38. Located in a cavity 41 in a depending portion ofmember 24 is a piston 42 forming with the cavity a double action aircylinder. Fittings 43 and 44 located at opposite sides of the cavity 41admit air supplied through hoses 48 and 49 alternately into each end ofthe cavity when a switch (not shown) is actuated.

The end of piston 42 is pivotably attached to connector 50 which ispivotably attached to links 51 and 52 by means of pin 53. The links arelikewise pivotably attached at their opposite ends to the extensions 35and 36 of the vertical supports 33 and 34 by means of pins 54 and 55respectively.

Thus, the hinged jaws 30 and 31 will be parted or opened when connector50 and piston 42- move away from the hinged jaws. This movement isaffected by permitting air to enter cavity 41 through fitting 43. Whenthe movement of the piston 42 is reversed by the delivery of air intothe position of the cavity 41 on the other side of piston 42 throughfitting 44, hinged jaws 30 and 31 will move toward each other aroundtheir pivot pins 37 and 38.

Each hinged jaw 30 and 31 comprises an elongated portion 58 terminatingin a semicircular portion 59. Semipair of semicircular portions 59 androtate within their own plane. Peripheral slots 65 and 66 are cutinpor'tion's' 59 and carry bolts 67 and 68 which are connected to plates61 and 62. The bolts 67 and 68 are attached to rod assemblies 70, one atthe side of each elongated member. As shown in FIGURE 7, each rodassembly 70 passes through a housing 71 which is also mounted on theelongated member 58 and which contains a spring assembly tending to holdeach of the plates 61 and 62 in a fixed angular position within itsmounting. Each spring assembly comprises a coiled spring 72 mountedwithin the housing 71 and so attached to each rod assembly 70 as toexert a force against any displacement of the rod. The position of therod assembly can be changed by means of a clamp 73 adjustably secured onthe rod 70.

In contrast, the rod assembly 74 extends through said housing a greaterdistance so that, when the motion of the transfer arm moves the jaws 30and 31 toward the mold, the rod extension 74 will abut an adjustablestop 77 mounted above the blow mold. Thus, force is exerted on the rodextension 70 by the stop 77 thereby imparting angular displacement tothe plate 62 which in turn displaces the other plate 61 overcoming thepositioning tendency of the pair of coiled springs 72. In this manner, aparison held between the plates 61 and 62 in a position as shown inFIGURE would be rotated about its longitudinal axis to a position asshown in FIGURE 6. When the transfer arm assembly is moved away from themold station, the spring assembly will return plates 61 and 62 to theiroriginal positions.

As shown in FIGURES 1 and 9, the adjustable stop 77 is attached to themold station frame by means of threaded bolt 82 engaging threadedopening 83 in the frame. By advancing bolt 82 with respect to opening83, the position of stop 77 can be moved relative to the parisontransfer arm. A rod 84 is mounted in an opening in the mold stationframe 10 and extends beyond the adjustable stop 77. Attached to one endof rod 84 is a conical tip 85 which is threadedly adjustable withrespect to rod 84 to permit movement thereof toward and away from thetransfer arm. When the transfer arm is in its retracted or lowermostposition, a conical female receptacle 86, mounted on member 24, contactstip 85 to stop the downward arcuate movement of the transfer arm.

The mold jaws 91 and 92 have lever extensions 93 and 94 pivotablyattached to support 11. Additional extensions 95 and 96 on each sideextend rearwardly of the mold and form clevis joints with ends ofmembers 97 and 98. The opposite ends of members 97 and 98 are pivotablyattached to a joining member 99 which is operably connected to an aircylinder 100. Mold halves 101 and 102 are removably attached between themold jaws 91 and 92 to permit replacement of the mold halves with moldsof other configuration for the production of articles having a differentsize, shape or weight.

As shown in FIGURES l, 10, 11, and 12, a member 105 having bifurcatedend 106 is secured to member 107 which is pivotably attached at itsupper end to members 108 and 109 in a clevis joint. Members 108 and 109are secured to support 104. Member 110 has a slot 111 shown in FIGURE 11and is pivotably attached at its lower end to members 112 and 113 whichstraddle support 104 in the same plane as members 108 and 109 and arepivotably attached to member 107. Joining member 99 is attached to a.piston rod of air cylinder 100 which operates the mold jaws. Extensions114 and 115, joined by a bar 116 at their ends, project outwardly fromjoining member 99 to permit engagement of bar 116 in slot 111 when thepiston rod of cylinder 100 is in its extended position as shown inFIGURE 12.

Thus, when a parison is transferred from an extruder to a mold stationin a freely swinging condition, the lower end portion of the parison isreceived by bifurcated end 106 of the positioner (FIGURE 10) andsteadied until the mold closes. As the mold closes, the parisonpositioner is withdrawn from between the mold halves and bar 116 isdisengaged from slot 111.

A blow stick 120, positioned directly below the mold halves, has itsvertical axis aligned with the longitudinal axis of a transferredparison. At the lower end of blow stick 120 is a cylinder 121 havingfittings 122 and 123 which' are connected to sources of low pressure andhigh pressure air (not shown). The blow stick 120 comprises a hollowmandrel having an upper tapered portion 124 and a lower cylindricalportion 125. Support 126 is attached to mold frame 10 and at its forkedend has a sleeve bearing 127 in which the blow stick is reciprocallymounted. Pivotably attached to frame 126 is a double action air cylinder129 arranged for arcuate movement at its opposite end. Piston rod 130 ofcylinder 129 is secured to member 131 which in turn is pivotablyattached to member 132. Member 132 is pivotably mounted upon frame 126so as to move member 133, pivotably attached at its upper end, downward.Member 133 is pivotably attached to one end of a clamp 134 secured tothe blow stick 120. A gear wheel 137 engages teeth 138 in the side ofblow stick 120 forming a rack and pinion arrangement to initially adjustthe height of the blow stick 120 with reference to the blow mold beforethe blow stick is clamped into position.

In the operation of the apparatus shown in the drawings, the transferarm moves in an arc path from its extended position below the extrudernozzle downward to a retracted position centered directly above the blowmold. The movement of the transfer arm in a downward motion minimizessagging or stretching of the parison during transfer. The parisonorienter portion of the transfer arm assembly grabs the parison from thextruder and rotates the parison about its longitudinal axis as theparison is being transferred to the mold station. The rotation of theparison is performed when it is desired to position an oblong orelliptical parison in a blow mold in a particular angular orientation.However, where a round parison with a uniformly thick periphery is beingmolded, a parison orienter of the type described above is not requiredand a simple pincers may be employed. Stop 77, mounted upon mold stationframe 10, can be adjusted toward or away from operating rods 44 of theparison orienter to increase or decrease the rotation of semicircularplates 61 and 62 for a particular mold station position.

The conical tip on stationary rod 84, which projects beyond adjustablestop 77, acts as a stop for the transfer arm assembly as it reaches itslower or retracted position. By means of the threaded connection betweenthe tip 85 and the rod 84, the mean rearward position of the transferarm can be adjusted to accurately position a parison within the mold.

When the upper portion of a parison is stopped abruptly by the contactof the transfer arm against tip 85, the lower portion of the parisonswings between the mold halves 101 and 102 and into contact withbifurcated end 106 on the end of the parison positioner. At this pointthe parison positioner is at its extended position. The bifurcated end106 steadies the lower portion of the parison until the tapered portion124 of the blow stick 120 embeds itself into the open lower end of theparison. The air cylinder then withdraws joining member 99 which bringsmold halves 101 and 102 together. As the mold halves move toward eachother, the parison positioner withdraws from between the mold halves.

It will be appreciated that proper positioning of a parison within ablow mold is an important feature of the present invention in order toproduce accurately molded hollow plastic articles. If the parison is notproperly positioned, application of fluid pressure to the interior ofthe parison will expand it unevenly and often result in holes ornonuniform wall thickness in the final article, thus increasing thenumber of rejects.

The above description shows that the method and apparatus of the presentinvention provide a simple and convenient means for producing hollowplastic articles such as containers or bottles at a substantially higherrate than has heretofore been possible. Further, the present inventionpermits the high extrusion rates of continuous extruders to beefficiently utilized. Moreover, the method and apparatus of theinvention permit great flexibility in the production of hollow plasticarticles varying Widely in size, shape, and weight. Also, the number ofrejects are minimized by the method and apparatus of the invention dueto the accuracy of alignment of the parison within the mold cavity.

From the above description of the invention, it will be apparent thatvarious modifications in the apparatus and procedure described in detailherein may be made within the scope of the invention. For example, thetransfer mechanism pincer jaws and parison positioner may be of adifferent design and operation while still achieving the advantages andbenefits of the invention. Therefore, the invention is not intended tobe limited to the specific details of procedure and apparatus describedherein except as may be required by the following claims.

What we claim is: 1. A method for forming hollow plastic articles byexpansion of a parison Within a closed sectional blow mold around thealigned parison, blowing the finished article, opening the sectionalmold and removing the article.

2. A method as set forth in claim 1 wherein the transfer movement isalong an arcuate path.

3. A method for forming hollow plastic articles by expansion of aparison within a sectional blow mold comprising extruding a parison at apoint above and laterally displaced from a sectional mold, grasping theparison at its upper portion and transferring it downwardly andoutwardly through an arcuate path to the open sectional mold, stoppingthe grasped portion of the parison in proper alignment with the opensectional mold, aligning the lower portion of the parison within theopen sectional mold by contacting it with the member protruding into theopen sectional mold, closing said sectional mold around the alignedparison while moving the aligning member outside of the sectional mold,and blowing the finished article.

References Cited UNITED STATES PATENTS 2,750,624 6/ 1956 Coates et al.26499 1,557,850 10/1925 La France -323 1,607,607 11/1926 Cramer 653232,750,625 6/1956 Coates et al. 26499 2,783,503 3/1957 Sherman 264992,935,764 5/1960 Mason 26498 2,978,745 4/1961 Langecker 264--993,000,051 9/1961 Schaich 26499 3,080,614 3/1963 Adams 26498 3,204,0188/1965 Hagen 26499 ROBERT F. WHITE, Primary Examiner.

A. R. NOE, Assistant Examiner.

1. A METHOD FOR FORMING HOLLOW PLASTIC ARTICLES BY EXPANSION OF APARISON WITHIN A CLOSED SECTIONAL BLOW MOLD COMPRISING THE STEPS OFGRASPING THE UPPER PORTION OF A HEATED PARISON AT A POSITION ABOVE ANDLATERALLY DISPLACED FROM A SECTIONAL MOLD, TRANSFERRING THE PARISONDOWNWARDLY AND OUTWARDLY TO THE OPEN SECTIONAL MOLD WITH THE INITIALPORTION OF THE TRANSFER MOVEMENT PRODUCING THE GREATER PORTION OF THEDOWNWARD MOVEMENT OF THE PARISON AND THE FINAL PORTION OF THE TRANSFERMOVEMENT PRODUCING THE GREATER PORTION OF THE LATERAL MOVEMENT OF THEPARISON, RAPIDLY STOPPING AND ALIGNING THE PARISON WITHIN THE OPENSECTIONAL MOLD, CLOSING THE SECTIONAL MOLD AROUND THE ALIGNED PARISON,BLOWING THE FINISHED ARTICLE, OPENING THE SECTIONAL MOLD AND REMOVINGTHE ARTICLE.